Wait I know why it happened:
lichess.org/forum/off-topic-discussion/seriously#4You see, someone put a hot object on top of the South Pole Neutrino observatory, causing the whole place to catch on fire. The fire hydrant soon caught on fire and the fire couldnt be put out so everyone escaped. There happened to be one person on lichess in the observatory when the fire started and he dropped his phone while being on opening explorer into the fire in the rush to hurry out.
From here on out, the story gets even crazier:
The people at the Neutrino Observatory had discovered this thing called "dimensional blend" which is a one-in-a-quintillion occurrence. They saw the behavior of small particles and came to the conclusion of the theoretical possibility of dimensional blend. But turned out that dimensional blend occurred at the wrong time. The fire spread from the observatory to the lichess opening explorer via dimensional blend, setting the entire opening explorer on fire. Then, the fire got out to the databases where lichess servers are held via someone else on lichess opening explorer who saw the fire. Again, dimensional blend occurred in Strasbourg and suddenly, the entire database bulding was on fire. Lichess was able to recover mostly normal operations because they were less affected, but turns out, the fire in the opening explorer couldn't be stopped yet because lichess couldn't find a way to insert an image of a fire hydrant to stop the fire in the opening explorer. However, they were able to contain the fire by putting a box around the opening explorer. The thing is: there was a fire hydrant in the opening explorer, but it caught on fire as well. But I've heard that lichess is trying to get a fire hydrant to stop the opening explorer fire still.